This invention is concerned with coding related sorting systems, methods and apparatus particularly useful in the agricultural industry. The sorting of agricultural commodities during or shortly following the time of their harvest has assumed increasing importance as an aspect in achieving both production economies and higher quality processing and packaging prior to the introduction of the commodities into the consumer market. Concerning the utilization of coding and sorting systems in conjunction with harvesting, the development of economical and efficient field sorting techniques for several agricultural commodities would be of considerable value to the industry. As one example, potatoes, by virtue of the soil conditions extant in the regions of their cultivation, are removed from the ground in conjunction with rocks, clods and the like which ultimately must be separated from the harvested material bulk. Typically, potatoes are harvested by a tractor-drawn mechanism having blades which are driven beneath the ground surface below the growth level of the potatoes and which serve to drive the potatoes, associated vines, rocks and earth clods upwardly. Chain-type conveyors mounted upon the harvester then transport the potatoes as well as the earth clods and rocks in a generally upwardly disposed direction and in a manner intended to achieve as much separation of the clods and rocks from the potatoes as is possible. Following passage through a devining position, additional harvester mounted conveyors move the potatoes with unseparated clods and rocks past hand separating stations. Depending upon field conditions at this point in the harvesting process, typically up to 50 percent of the harvested bulk will be present as rocks and clods. Usually, three to five farm laborers ride the harvester to man the sorting stations and attempt to remove the rocks and clods from the conveyors by hand. With the increasing speeds of harvester movement now employed in the harvesting procedures (i.e. three to five miles per hour), the exertions of field hand labor are inadequate to achieve substantial sorting. As of consequence, the potato harvest conveyed from the sorting stations to trucks intended for transporting the materials to warehouses will exhibit a rock and clod content typically in the range of 20 percent and more of the bulk thereof. Upon being trucked to storage facilities, the potatoes subsequently are hand sorted to remove damaged or rotted potatoes, rocks and clods prior to bagging and sale. The latter occurrence of damaged and rotted potatoes is considered to be at least in part due to the transporting of unseparated rocks and potatoes into trucks during harvesting, the rocks falling with the potatoes from position to position and causing damage. Resort to later sorting of substantial quantities of rocks and earth at the storage facilities contributes two cost factors to the harvest, that associated with sorting itself and that involved in removing and disposing the not insignificant quantities of rock and earth generated by the last sorting step. The tonnage of soil maneuvered in the course of potato harvesting provides some insight into the quantities under consideration. Harvesting two rows of vines at a speed of two miles per hour with digger blades set at a depth of four inches means that the harvester aprons are lifting an average of six to ten tons of soil per minute.
The procedures for harvesting onions are somewhat similar, the environment within which the machinery is required to operate being rigorous and dirty, as is the case with potato harvesting. Generally, the quantity of rocks and earth clods removed with onions during the harvesting thereof is considerably greater than that associated with potato harvesting as described above. Typically, 50 percent or more of the bulk of the onion harvest will be present as rocks and clods.
As is apparent, in either harvesting procedure, where removal or sorting procedures are carried out at processing or collection stations removed from the locale of the producing fields, higher expenditures are necessitated for hauling the greater weight and bulk of the harvest. Conversely, where rock materials and the like can be removed at the site of the harvest, disposal problems associated with waste are minimized and the cost of transporting the harvested product to collection regions or stations is considerably lower. By separating the dirt clods early or in conjunction with the harvesting procedure itself, convenience and economy readily are recognized. As is apparent, a separating system mounted upon the harvester itself which is capable of efficiently identifying or coding both rock and earth clods and separating them from potatoes or onions will be of considerable value to the agricultural industry. To be practical, however, such a sorting system must be capable of operating efficiently under the dirty and rigorous conditions extant in a harvesting environment.
Perhaps one of the more complex harvesting techniques is associated with the tomato. Currently, about 300,000 acres in California and a smaller but significant number in the midwest are devoted to the production of processing tomatoes. Substantially all of the California acreage is machine harvested, while about 10% of the acreage in the midwestern locale is so harvested. Presently grown tomato cultivars ripen non-uniformly and, as a consequence, they either must be harvested by hand as they ripen, or, if practical, once-over mechanical harvesters are employed, the tomatoes all being harvested at one time and the resultant harvest providing a bulk quantity thereof which must subsequently be sorted to remove green or immature fruit. Particularly in consequence of labor related economic factors, the industry has looked with favor toward harvesting procedures of the once-over variety wherein the vines are uprooted, all tomatoes removed therefrom and transported to collection stations for packing house processing. Where field sorting of the tomatoes in accordance with their degree of ripeness is provided, such provision generally is made through the utilization in the field of about ten to twenty-five laborers who ride upon the harvester to carry out visual coding and sorting. The consequent labor expense as well as the significant increase in machine size and weight have been found to impose severe limitations on the effectiveness of the mechanical harvesting system. Size and weight are particularly complicating factors where the harvesters are utilized in wet or soggy fields, an environmental condition very often encountered in the midwestern regions. For a more detailed discussion of the latter problems, reference is made to the following publication:
I. Harbage, R. P., T. H. Short, and Dale W. Kretchman, (1972). Considerations for Mechanizing Processing Tomato Production in Ohio. Agricultural Engineering Series 12, Ohio Agricultural Research and Development Center, Wooster, Ohio. PA1 II. Stephenson, K. Q. (1974). Color Sorting System for Tomatoes. Transactions of ASAE, 55: 1185. PA1 III. Johnson, Paul E. (1973). Tomato Harvesters for the Midwest. Unpublished paper. Agricultural Extension Service, Purdue University. PA1 IV. Wright, Paul L. (1972). The Latest on Machine Harvesting of Processing Tomatoes in Ohio. Unpublished paper, Agricultural Extension Service, Fremont, Ohio. PA1 V. Kattan, A. A., R. H. Benedict, G. A. Albritton, H. F. Osborne, and C. Q. Sharp. (1968). Mass Grading Machine-Harvested Tomatoes. Arkansas Farm Research, Vol. XVIII, No. 1, January-February, 1968, p. 5. PA1 VI. Kattan, A. A., C. Q. Sharp, and J. R. Morris. (1969). A Mechanical Sorter for Tomatoes. Arkansas Farm Research, Vol. XVIII, No. 1, p. 8, January-February, 1969.* FNT *See Also: Gould, W. A. "Mass Sorting of Mechanically Harvested Tomatoes." Research Circular 209, December, 1975. Ohio Agricultural Research and Development Center, Wooster, Ohio. PA1 VII. Heron, J. R. and G. L. Zachariah. (1974). Automatic Sorting of Processing Tomatoes. Transactions of ASAE, 55: 987. PA1 VIII. Stephenson, K. Q. (1964), Selective Fruit Separation for Mechanical Tomato Harvester. Agricultural Engineering, 45: 250-253, May, 1964. PA1 IX. Stephenson, K. Q. (1966). Automatic Sorting System for Tomato Harvesters. Procedures of National Conference on Mechanization of Tomato Production, Purdue University, Lafayette, Indiana. 1966. PA1 X. Hamann, Donald D. and Daniel E. Carroll. (1971). Ripeness Sorting of Muscadine Grapes by Use of Low-Frequency Vibrational Energy. Journal of Food Science, 36: 1049. PA1 XI. Hamann, D. D., L. J. Kushman, and W. E. Ballinger. (1973). Sorting Blueberries for Quality by Vibration. Journal of the American Society for Horticultural Science, Vol. 98, No. 6, p. 572-576, Nov., 1973. PA1 XII. Stephenson, K. Q., R. K. Byler, and M. A. Wittman. (1973). Vibrational Response Properties as Sorting Criteria for Tomatoes. Transactions Of ASAE, 16: 258, March, 1973.
Where the extent of acreage involved in a given harvesting region is sufficiently large, more expensive machinery incorporating complete sorting systems becomes more practical, however, particularly in midwestern regions and the like, such cost considerations generally have precluded the utilization of harvesting systems incorporating automatic sorting devices. However, the need remains for a practical embodiment of a harvester mounted sorting system inasmuch as typical tomato cultivars do not ripen uniformly. Consequently, once-over harvesting procedures necessitate the collection of tomatoes of a broad variety of maturities including immature fruits, the value of which is considered dismissible. This situation is particularly prevalent in the midwest where mechanical harvesting commences when about 30% or more of the fruit is green or immature. Additionally, rainfall during harvesting periods is generally found to be higher in the midwest than in other regions, thus creating wet ground conditions which, as noted above, hinder movement of the harvesters in the field. This climate also asserts greater variation in the maturity range of a harvester crop. Further information concerning such harvesting aspects may be found in Publication I and the following publication:
Several varieties of tomato harvesters are currently produced, the capacity for more current models being in the range of about thirty tons of fruit per hour. Where manual sorting is incorporated with the machine, such capacities are considerably limited. Human sorting has been found to average about one-half ton per hour on a per capita designated basis. As is apparent, some other form of sorting is required to improve sorting capacities. For further discussion concerning the above harvesting considerations, reference is made to Publication I and the following Publication
In view of the significant quantity of machine picked tomatoes which are immature or green, and which have no significantly discernible value, a considerable advantage would accrue with the utilization of an economic field harvesting scheme automatically disposing of such tomatoes in the field site for natural biodegradation. Without such sorting, all harvested tomatoes are required to be hauled to the processing plant for sorting purposes, a requirement which levies higher costs upon the harvesting procedure.
Looking now to in-plant sorting techniques, typical sorting systems involve a non-destructive coding followed by a segregation technique sometimes referred to as "switching". While most industrial sorting procedures for comestibles are carried out by labor utilizing both the visual as well as tactile senses, investigations have been conducted into techniques for reducing the labor intensity of such procedures. For example, with respect to tomatoes, the specific gravity thereof has been found to increase with ripeness and has been suggested as a sorting technique. In one such arrangement, a gravity sorting system is provided wherein tomatoes are floated in solutions of ethanol and water. Typically eighty to ninety percent of the green tomatoes and fifteen to twenty-five percent of lower quality acceptable tomatoes will float. In another such arrangement, a low percentage brine solution has been utilized in an arrangement wherein the rate of upward floatation movement of tomatoes served as the coding procedure. For further information concerning such coding and sorting techniques reference is made to the following publications:
Sorting concepts for tomatoes based upon the light reflectance properties thereof have been proposed or developed as apparatus, for instance, electronic color sorters wherein light reflecting from the fruit is sensed by a photoresponsive device. Utilizing appropriate coding or selecting circuitry, a form of switching then is incorporated with the sorting system such as an air blast or plunger providing an ejection function. These systems are available only at such relatively higher costs as are considered above the level of practicality for plant or field installations of smaller extent. For field harvesting adaptation, the electronic or light reflectance systems are called upon to operate under somewhat rigorous and dirty field conditions. Accordingly, maintenance costs of considerable extent necessarily are encountered in addition to a relatively high initial capital investment. Further elaboration upon this form of sorting for tomatoes is provided, for example, in Publication II and in the following publications:
Investigations also have been conducted into the response of tomatoes and other fruits to vibrational phenomena. For example, a downwardly inclined trough mechanically excited by an electrodynamic shaker utilized for the purpose of separating grapes into ripeness categories has been described in U.S. Pat. No. 3,680,694 as well as in the following publication:
This same approach has been used in similar attempts to sort blueberries as described in the following publication:
The above studies generally recognize that vibrational sorting is based upon differences in resiliency of the object subjected to such vibration and that correlations are available between fruit or vegetable ripeness and this exhibited resiliency. The response of tomatoes to vibration as a potential criterion for sorting has been studied. For instance, the resonant frequencies of tomatoes of various maturities has been investigated, the response of a green tomato so excited being found to be approximately six times that of a ripe tomato. A more detailed discourse concerning this subject is provided in the following publication:
To the present time, sorters operating upon vibrational principles have been found to be somewhat impractical, their capacities for field harvesting applications being considered too low for the volumes of sorting usually required, and the mechanisms generating required vibration being both expensive and difficult to use at requisite frequencies.